In recent years, various types of electrical controls are used in a vehicle for achieving improvement in fuel consumption, safety, convenience or the like. That is, areas of functionality of electric control units (ECUs) are broadened and the number of the features in the ECU is increasing.
Further, the ECUs in the vehicle are interconnected with each other through a wired/wireless network for the exchange of control data and interactive operation. This kind of network is a so-called vehicle LAN.
Each of those ECUs is used for controlling a specific mechanism in the vehicle, and thus is named after its function. That is, the types of ECUs includes an engine ECU for controlling an engine, a cruise control ECU for controlling vehicle speed and an inter-vehicle distance, a transmission ECU for controlling an automatic transmission and the like. The scheme of the use of the ECUs for the vehicle are disclosed in Japanese Patent Document No. JP-A-2004-136816.
However, the ECU dedicated for a specific purpose is in-flexible in terms of a change/modification in the ECU, because of a rigid combination of circuits used therein and/or other restrictions. That is, a partial change of the ECU function leads to an entire re-designing of the specification, or a delay in the development schedule. The re-designing and re-scheduling of ECU development cause an increased cost of production.
For example, the ECU used for a cruise control system has two main functions, that is, a function for maintaining a constant speed of a subject vehicle and a function for maintaining a constant inter-vehicle distance toward a preceding vehicle. In this case, the speed maintaining function in the cruise control ECU is fully developed that the implementation of the speed maintaining function in the ECU does not have to be changed in the future, while the inter-vehicle distance maintaining function may incorporate changes in terms of, for example, an improved algorithms for distance detection and a modification of the sensors used for distance detection. This kind of changes in the specification of an ECU and/or the sensing/actuating device connected thereto lead to a change of the design of the entire ECU.